Warning--this video is pretty grotesque and unsettling -
What about the potential for a brain transplant? Wikipedia explains this well:
"One of the most significant barriers to the procedure is the inability of nerve tissue to heal properly; scarred nerve tissue does not transmit signals well (this is why a spinal cord injury is so devastating). However, recent research at the Wistar Institute of the University of Pennsylvania involving tissue-regenerating mice (known as MRL mice) may provide pointers for further research as to how to regenerate nerves without scarring.
There is also a potential problem of the new interface at the spinal cord, in that even if all the nerves are connected successfully, they may still be connected wrongly, in some cases, thus not transmitting the same information as the same nerve connection in the old body. For example, a nerve that used to control the right index finger's muscle group might be connected to a different finger's muscle group, or another body part entirely. If this were to happen to a large number of connections, the person undergoing the transplant might end up with a body which transmitted sensory input to the wrong destination, making it incomprehensible and potentially requiring many years of rehabilitation.
Also, for the procedure to be practical, the age of the donated body must be sufficient: an adult brain cannot fit into a skull that has not reached its full growth, which occurs at age 9–12 years.
There is an advantage however, the brain is an immunologically privileged organ, so rejection would not be a problem, unlike other organs, say the liver, which is usually aggressively rejected by the host's immune system."
The made-for-tv awesome movie "Who Is Julia?" (it can be found for free on YouTube) was an excellent hypothetical case. Two women in an accident. The beautiful model's body is ruined, but her brain is alive. The plain jane wife and mother's body is intact, but her brain is dead. Put the model's brain into the wife's body and you get confusion as to who she is-for her and her family members!
Eventually, this could be possible, but any technology we come up with would likely make it possible to regenerate the tissue that is lost, whether it's brain or spinal cord rather than put someone's brain into another body.